This invention relates to an apparatus for testing power transmission belts, and more particularly to a type thereof in which a drive belt and a test belt are subject to constant load and slippage by the rotational ratio differential between the drive and test belts. The apparatus is particularly effective for testing frictional power transmission belts such as a V-belt, flat belt, roundish belt, and poly-V-belt having a zig-zag pattern in cross section at the inner surface thereof, or a synchronous transmission belt such as a toothed belt.
According to the conventional apparatus of this type, a constant load is applied to the shaft of a drive pulley. For example, as shown in FIG. 1, a water wheel 6 is connected to a driven shaft 2 which is connected to a driven pulley B.sub.1 in order to provide a constant load by pouring a constant amount of water onto the water wheel. A test belt 3 is mounted between the driven pulley B.sub.1 and a drive pulley A.sub.1 which is connected to a drive shaft 1 connected to a driving means 5. This apparatus is a so called "water brake" system, according to which the test belt 3 is subjected to a load due to the rotational timing (r.p.m) differential between the pulleys A.sub.1 and B.sub.1.
Another type of conventional apparatus has been proposed, in which an electrical brake is applied to the driven side to apply load to the test belt. However, in both cases, the load is obtained by the external means, such as the water wheel and the electrical brake, and therefore, power consumption would be very large, and uneconomical apparatuses would result.
In order to obviate these drawbacks, U.S. Pat. No. 3,739,632 discloses that a hydraulic rotary actuator is provided to one of the shafts to apply to the belt. However, according to this apparatus, though torque of the shaft can be easily changed, the hydraulic rotary actuator may not sustain high power, so that the belt testing operation cannot be conducted under all conditions.
Further, U.S. Pat. No. 3,956,929 discloses that one of the belts is a variable speed belt mounted between first ends of two shafts disposed in parallel and the other belt is mounted between the other ends of the shafts. Tension applied to the other belt is controlled by the variable speed belt. However, this apparatus has drawbacks in that torque applied to the test belt is disadvantageously changed. Further, the variable speed belt is required to be replaced with the another one in conformity with the length of the test belt.